Two teams of British and Canadian scientists have created human cells directly from the skin of a patient, eliminating the need for embryos.
The results of the investigations of both teams, announced by the journal Nature, are an important step in the search for safe treatments for the replacement of damaged tissue of any part of the body.
Properly handled by the scientists, skin cells take on the properties of stem cells from embryos normally so they can become any tissue in the body.
Previously it was only possible to create these induced pluripotent stem cells (initials in English: iPS) using viruses to insert four genes that perform the reprogramming.
But the modified virus DNA in the cells so that increased the risk of cancer, so the technique was too risky for use in human patients.
Another danger that existed was that the changes caused by genes would lead to developmental abnormalities.
But now, scientists have managed to avoid the use of viruses and remove genes once they have fulfilled their task.
British and Canadian teams were able to insert four genes into a single segment of DNA to carry out the necessary reprogramming and then removed before they could cause damage.